There is a newly published resource that every apologist will want in his library: Heinrich Denzinger's Compendium of Creeds, Definitions, and Declarations on Matters of Faith and Morals. This reference book is a sorely needed English update to one of the richest compendiums of Catholic doctrine ever compiled.

Commonly referred to simply as Denzinger (after the German theologian who published it in 1854) this doctrinal compendium...